Re: Simm compatibility for Apple IIgs ram cards - potential FAQ addition

["William Garber" <willy46pa@garberstreet.com>]

"roughana" <andrew.roughan@writeme.com> wrote in message 1177080936.759464.59300@n59g2000hsh.googlegroups.com">news:1177080936.759464.59300@n59g2000hsh.googlegroups.com...
: I have a whole heap of Simms from an unknown source.
: How can I tell if they should work in a IIgs RAM card or not?
: (The answer to the following questions would be a great addition to
: the CSA2 Hardware Hacking FAQ - I didn't see anything like this in
: there.)
:
: I've done some searching on chip numbers in google to determine what
: the individual chip capacity is. This can be used to calculate what
: the simm capacity is.
:  e.g. there are 8 * 256x1 chips on the simm -> 256k capacity
: there are 9 * 256x1 chips on the simm -> 256k with parity
: 2 * 1Mx4 (Number of Words = 1M, Bits Per Word = 4)  -> 1MB capacity
: 8 * 1Mx1 -> 1MB
: 9 * 1Mx1 -> 1MB with parity
:
: Is there any general rule that 2/3 chip simms don't work and that you
: need to use 8/9 chip simms?
:
: Another post on this topic indicated that the simm must support CAS
: before RAS refresh. I haven't yet found this type of information for
: any chip that I have searched on so far. How can this be determined?
: e.g. available spec sheet info for one chip is
: http://www.datasheets.org.uk/specsheet.php?part=GM71C4400AJ70
:
: Should there be a spec sheet for the simm itself?
:
: What RAM cards exist that use simms?
: OctoRAM (MDIdeas), Sirius RAM, GS-Sauce, Q-RAM GS, Megaram (4MB card
: made by Scarlan Computing Services in Australia), any others?

Also, the RAM-4-GS by Garberstreet Electronics.

: Maximum capacity of a simm that is supported by any of these cards is
: 1MB. So don't bother trying higher capacity simms (2MB, 4MB etc)
:
: I've tried a few simms that did not allow me to boot GS/OS. Variety of
: symptoms: Fatal error 681; thermometer doesn't move etc. Then I tried
: 4 * (1MB capacity with parity) simms in my Megaram card and GS/OS
: boots but then I get an error when I try to do something in Finder.
: Why is this? Bad refresh? Bad RAM chip?

Speed, maybe? It's been my experience that anything
faster than 70ns is hit or miss. Also be sure that
the speed of all of the simms is close, particularly
adjacent pairs being equal.

: All enlightenment greatly appreciated.
:
: Cheers,
: Andrew

William Garber
Email Address - willy46pa@garberstreet.com
Alt. Email - willy46pa@comcast.net
Web address - http://www.garberstreet.com